Doppler ultrasound is relied upon as the primary and often the only test used to diagnose vascular pathology. Because variations in technical skill directly impact surgical referral decisions, there is a strong clinical need to ensure that provides both attain and maintain skills in this procedure. The problem we address is the lack of a quantitative or standardized method for assessing skill in Doppler ultrasound during or following training. Our objective in Phase II is to develop and validate a simulator of vascular Doppler ultrasound, for simulator-based competency testing. The features of our simulator make it uniquely suitable for competency testing because it 1) enables realistic testing of the clinical procedure without requiring live patients, and 2) reports objective and quantitative metrics not only of cognitive skill (knowledge) but also of psychomotor (technical) skill in performing image acquisition. These features are unique to our technology. The ultimate aim of this proposal is to bring our simulator from prototype to fully- operational, and to demonstrate its validity for ultrasound skill assessment. That demonstration will prove the feasibility of simulator-based competency testing as well as bring this new technology to meet the requirements of professional societies that perform certification. Our Specific Aims are: Aim #1: To develop test modules for three blood vessels whose diagnosis depends on Doppler ultrasound examinations. Aim #2: To complete the validation of our simulator for competency-testing. There are five types of validation evidence. We demonstrated simulation accuracy in Phase I. We will collect the remaining evidence in Phase II. Aim #3: To convert the software developed in Phase I from prototype to production quality code to give our simulator the reliability essential for high-stake certification testing.